Will audio render in sync, like when previewing in textured or solid mode?
It will not render it at the slower speed. However, there is a way you could be able to get around this.


Just look in the upper left corner of the 3D view while the animation is playing, and get its approximate frame rate. (average the values it changes to). [this number is the framerate the animation is playing at due to lag]





Now choose a "custom" as the framerate and set the FPS to that average.





Alternatively you can use time remapping to adjust the "speed" while still sticking to the target framerate.


This is not the optimal way to do things, and it will not work perfectly, but it is the only way (that I know of) to do what you are asking. Also note that to render it how it looks in the viewport (but at the proper frame rate) use open GL render.



Unfortunately, this framerate lag is natural, and there isn't much of a way to fix it. If your computer is not fast enough and can not handle processing the info for each frame that fast, it will have to slow down. Here is a picture of my quadcore's (8 thread) workload while running a 1,000,000 particle simulation. The FPS lagged down to 7.



The arrow is where I stopped the simulation before starting it again. The only way to fix this is to simplify your scene to make it run faster, or use compensations that will help speed things up, like viewing in solid view-port mode. If you move objects that are not necessary while animating to other layers, and have those layers hidden, this will also help. You can also simply hide objects.

There is a good way to avoid this in the future though!

Us the A/V sync feature (audio/video sync)


In the timline, open the "sync" menu.
Change it to "AV Sync"